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Frightening movies or TV shows, like "The Haunting of Hill House,” can trigger a fainting response in people.

Netflix/Everett Collection

October 29, 2018

The Netflix original horror series The Haunting of Hill House is so good, according to some viewers, that it’s scaring them sick. While the claims on social media may be an exaggeration, there is a medical reason why certain triggers, such as fear or the sight of blood, can cause a brief loss of consciousness.

A modern take on the 1959 novel of the same name, the 10-part Hill House series debuted on October 12, 2018. Since then, fans have taken to Twitter with reports of nausea and fainting. Such behavior may be the result of a phenomenon known as vasovagal syncope, a stress response in which a person’s heart rate and blood pressure drop suddenly.

“Over 50 percent of patients who come in [to see me] for fainting have the vasovagal variety, which is based on the activity of a hyperactive nerve,” says Bryant Lin, MD, an internist who specializes in syncope at Stanford Health Care in Palo Alto, California.

What Causes Vasovagal Syncope?

Vasovagal syncope is a loss of consciousness resulting from a stress- or pain-related response by the body’s vagus nerve.

The vagus nerve is the master control center for life-sustaining autonomic processes, such as breathing and heartbeat. It is the longest cranial nerve and operates as a switch for unconscious reactions to threats in the environment

As opposed to the fight-or-flight response, in which the body girds itself for battle or to escape danger, vasovagal syncope slows down bodily functions. Blood pressure and heart rate drop, and consciousness slips away as blood flow to the brain diminishes. When the individual faints and falls to the ground, gravity helps restore cerebral blood flow.

Stephen Porges, PhD, the Distinguished University Scientist at Indiana University in Bloomington, describes it as a “freeze or faint” response.

According to Martha Gulati, MD, cardiologist at the University of Arizona in Phoenix, vasovagal syncope may seem “counter-evolutionary” as a stress response. “When I say ‘boo,’ your blood pressure should go up, your heart rate should quicken, and you should prepare to flee or fight,” she says.

But Dr. Porges sees it differently. “It’s something you’ll see, for instance, after a plane crash, when some people will scream, some will become agitated, and others will faint,” he says. “It’s not that it’s good or bad. It’s all just part of our genetic complexity.”

“Fainters are safer than most people realize,” says Robert Sheldon, MD, a cardiologist with the University of Calgary in Alberta, who writes Canada’s annual medical guidelines for syncope treatment.

“One-third of your friends and one-half of your doctors have fainted,” Dr. Sheldon says. “Yet only 1 faint in 7 leads to any injury, mostly bumps and bruises from falling. Only 1 in 100 causes a broken bone or skull injury.”

Nonetheless, serious injury can occur whenever a person loses consciousness, and fainting may signal an underlying heart or brain condition.

Managing Fear and Vasovagal Syncope

There are some things that you can do to reduce the risk of a drop in blood pressure and heart rate that causes fainting:

Make sure you’re adequately hydrated.

Too little sodium can cause dizziness, so have a salty snack or a salt pill.

Compression socks can help promote blood flow.

If you feel dizzy, put your head between your knees.

Remain seated or lie down.

Take slow, deep breaths.

Medical practitioners are not exempt from common fears and fainting. Dr. Gulati, for example, has learned to cope with her own fear of needles.

“I know that I’m prone to passing out, so I stay well-hydrated, I try to distract myself, I look away from the needle, and I make sure I have eaten something salty,” she says.

The son of “two fainters,” Sheldon says a full faint can be avoided by attending carefully to the prodrome — the warning signs that an attack is imminent.

Light-headedness, dizziness, unsteadiness, “seeing stars,” or a feeling of nausea can signal an oncoming loss of consciousness.

These all are signs that phlebotomists, who are trained to draw blood for clinical and donation purposes, know to watch for during blood donations.

“When we see fainting, it’s mostly among young people,” says Ross Herron, MD, the chief medical officer of the Western division of the American Red Cross in Los Angeles, “So we train everybody to look for signs and to ensure donors remain quiet and seated after giving blood.”

When it comes to scary movies or TV shows, the best preventive measure for some people may be to just watch something else.

“Scary shows [like Hill House] do a great job,” says Porges. “Viewers may have to relearn their own limits.”